Question: $ { \left[\begin{array}{rr}{2} & {1} \\ {3} & {-1} \\ {4} & {0}\end{array}\right]+\left[\begin{array}{rr}{2} & {-1} \\ {-1} & {2} \\ {-1} & {0}\end{array}\right] = {?} } $
Solution: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{2}+{2} & {1}+{-1} \\ {3}+{-1} & {-1}+{2} \\ {4}+{-1} & {0}+{0}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{4} & {0} \\ {2} & {1} \\ {3} & {0}\end{array}\right]}$